The present invention relates to orthoester-based surfactants. More particularly, the present invention relates to treatment fluids comprising orthoester-based surfactants and associated methods.
Surfactants may be used in a variety of applications. Such applications may be above or below ground, for example, in a subterranean formation penetrated by a well bore. Where used in above-ground applications, surfactants may be used, for example, to emulsify an oleaginous fluid (e.g., a heavy oil) to facilitate transport in a pipeline. Surfactants also may be used in subterranean applications, for example, in drilling operations, stimulation treatments (e.g., fracturing treatments), well bore cleanups, viscous sweeps, and completion operations (e.g., sand control treatments, gravel packing). In these applications, the surfactants may be used for a number of purposes, including as emulsifying agents, non-emulsifying agents, foaming agents, defoaming agents, dispersants, wetting agents, and the like.
While a variety of surfactants have been used in subterranean applications, problems have been associated with their use. For instance, certain surfactants used heretofore may have undesirable environmental characteristics and/or may be limited by strict environmental regulations in certain areas of the world. Thus, degradable surfactants have been used to reduce the potential for bioaccumulation and/or persistence of such surfactants in the environment. Currently available degradable surfactants, such as esters, amides, and acetals, have characteristics that may limit their usefulness in subterranean applications. For instance, esters and amides may not degrade as desired in conditions that may be encountered downhole. Further, degradation of esters and amides is slowest at pHs encountered in the subterranean environment, and thus may result in unacceptably long persistence times. Likewise, problems also may be encountered with the use of acetals in subterranean applications. While acetals are usually stable at high pH values (e.g., > about 6), low pH values (e.g., about 1-4) may be required for their degradation to occur at desirable rates. This typically requires exposure of the surfactant to an acid to facilitate the degradation thereof after introduction into the subterranean formation, which may add undesired expense and complexity to the subterranean application.